Shear clamp



April 1968 M. H. BECKMAN 3,377,763

SHEAR CLAMP Filed Nov. 8, 1965 I United States Patent "ice 3,377,763 SHEAR CLAMP Melvin H. Beckman, Rockford, Ill., assignor to National Lock Co., Rockford, Ill., a corporation of Delaware Filed Nov. 8, 1965, Ser. No. 506,813 7 Claims. (Cl. 52-584) ABSTRACT OF THE DISCLOSURE A shear clamp retaining two adjoining precast concrete units together, where the concrete units have central cylindrical voids therein, including a base portion extending between the voids in the concrete units and terminating at each end in an integral jaw extending The present invention relates to a mechanical device forv preventing lateral movement of end units or slabs of a'precast concrete unit system and more particularly to a novel shear clamp utilized to join adjacent concrete slabs 'by application of the clamp at the ends of the slab to prevent lateral movement and differential deflection between two adjoining slabs. Such application merely requires the use of a hand tool.

In present methods of placing precast concrete units or slabs in a floor or root system, the end units of the system often move laterally away from the main mass of the building due to the fact that these end units usually bear partially on the end wall and are supported by this wall, and the inner slabs tend to deflect more as they do not have this support. Also, due to plastic flow in the concrete and to different types of loading, differential deflection occurs which produces a horizontal force acting against the grout key between the end and inner units. The lateral movement of the end slab or unit in a direction away from the inner unit often cracks the end wall or the end wall veneer material. Also, the de fiection of the inner units, which is usually more than the end slab causes cracking, separation and uneveness in the floor or roof and also in the ceiling between the inner units and the end unit.

The present method of preventing or minimizing lateral movement of the end units is to cut open the top of the end unit and one or more inner units, the cut extending laterally or across the units, place one or more reinforcing rods in the cut and fill the cut with concrete or grout. This ties the end unit to adjacent inner units so that deflection of the end and inner units is the same and lateral movement of the end unit is prevented. However, this procedure requires substantial time and effort. The present invention obviates the necessity of cutting the top of the precast concrete units, placement of reinforcing rods, pouring of concrete and waiting for the concrete to cure by using a clamping member to join adjacent units, thereby effecting a substantial saving in time and money avoiding the necessity of being dependent on weather conditions.

Among the objects of the present invention is the provision of a shear clamp which is placed in the voids of adjacent concrete units and then by mechanical action, firmly clamps the device in place. The shear clamp is 3,377,763 Patented Apr. 16, 1968 utilized at the ends of the precast concrete units and clamping action is produced by the use of hand tools.

Another object of the present invention is the provision of a shear clamp formed of metal which will fit loosely into the voids in concrete units and then is firmly clamped in place. The clamp has a generally C-shapc and includes threaded means with clamping occurring by operating the threaded portions of the clamp assembly.

A further object of the present invention is the provision of a shear clamp having a base portion with clamping jaws at the opposite ends. One jaw includes an intermediate angularly disposed portion having an opening therein and a clamping portion perpendicular to the intermediate portion. A threaded bolt extends through an embossment on the base and the intermediate portion and .threadingly engages a nut behind the intermediate portibn so that operation of the bolt will draw the clamping portion of the jaw into engagement with the concrete unit.

Further objects are to provide a construction of maximum? simplicity, efiiciency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.

In the drawing:

FIG. 1 is a fragmentary perspective view of a plurality of precast concrete units or slabs forming a floor or roof and joined by the shear clamps of the present invention.

FIG. 2 is an enlarged front elevational view of the shear clamp applied to a pair of adjoining concrete units.

FIG. 3 is an end view of the shear clamp applied to a concrete unit taken from the right-hand end of the clamp of FIG. 2.

FIG. 4 is an end view of the opposite end of the shear clamp.

FIG. 5 is a horizontal cross sectional view of the shear clamp taken on the line 55 of FIG. 2.

FIG. 6 is an enlarged top plan view of the shear clamp prior to actuating the bolt to clamp the device onto adjoining concrete units.

Referring more particularly to the disclosure in the drawing wherein is shown an illustrative embodiment of the present invention, FIG. 1 discloses a plurality of precast concrete units or slabs forming a floor or roof assembly including an end slab 10 and inner slabs 11, each slab having one or more longitudinal voids 12 formed therein extending longitudinally through the slab. Furthermore, each slab is provided with recesses in the edges thereof which are filled with grout after the slabs are assembled to form grout keys 13.

A shear clamp 14 having a base portion 15 and a pair of projecting jaws 16 and 17 extend across each grout key 13 with the jaws extending into the voids 12 of the adjoining open-ended slabs to clamp these slabs together. As more clearly shown in FIGS. 2 to 6, the shear clamp 14 includes the fiat base portion 15 having a circular embossment 18 with an opening 19 formed adjacent one end of the base and aligned with the void 12 in inner slab 11 but offset from the axis of the void.

The jaw 16 has a generally arcuate surface corresponding to the curvature of the wall surface or interior of the void 12 in the end slab 10, and the convex or arcuate clamping surface 21 of the jaw 16 is provided with one or more projections or points 22 formed thereon to project against and engage the wall of the void 12 and retain the clamp 14 on the slab 10. The jaw 17 is provided with a short portion 23 perpendicular to the base 15 and an inwardly, angularly disposed portion 24 having a generally square emboss-ment 25 therein; the portion 24 being at an obtuse angle to the portion 23. A curved or arcuate clamping portion 26 extends inwardly into the void 12 of slab 11 perpendicular to the portion 24, and the convex surfiace of the clamping portion 26 includes one or more projections or points 27 like the projections 22 on the jaw 16.

A square internally threaded nut 28 is positioned within and held against rotation in the recess of embossment 25 at the rear of the angularly disposed portion 24 and a bolt 29 extends angularly through the opening 19 in embossment 18 and a central opening in embossment 25 and threadingly engages the nut 28. The shear clamp 14 is shown in its normal inactive position in FIG. 6 prior to engagement with two adjoining open-ended slabs 10 and 11. The clamp is positioned at the end of the slabs 10 and 11 with the jaws 16 and 17 extending into the voids 12 of the slabs. To clamp the slabs together, the bolt 29 is rotated to draw the nut 28 inward towards the exposed head 31 of the bolt. The action of the bolt and nut causes the angularly disposed portion 24 of the jaw 17 to be drawn inwardly; the jaw 17 bending or flexing at the juncture of portions 23 and 24. When the portion 24 has been drawn to a position substantially parallel to the base portion (see FIG. 5), the jaw 16 and the clamping portion 26 of jaw 17 are drawn into engagement with the slabs with the projections or points 22 and 27 engaging the surfaces defining the adjoining voids 12 and thereby retaining the clamp and slabs against movement.

Obviously, the size, shape and structural qualities of the shear clamp 14 will be determined by job conditions, the configuration of the precast concrete units andthe lateral forces to be resisted. By preventing lateral movement between adjacent slabs, the grout key 13 will act as a shear preventor and in so doing will prevent as a secondary effect the differential deflection between the inner and end slabs or units.

Having thus disclosed the invention, I claim:

1. A shear clamp retaining a pair of adjoining precast slabs such as concrete having voids therein against lateral movement, comprising a base portion and an integral jaw at each end of the base portion extending into the voids in the precast slabs, one jaw being substantially perpendicular to said base portion and the opposite jaw having an angularly disposed portion extending inwardly toward the first mentioned jaw and a clamping portion extending substantially perpendicular to said angularly disposed portion, and means extending between the base portion and the angularly disposed inwardly extending portion for drawing said angularly disposed portion toward said base portion and clamping the jaws against the surfaces of the adjoining slabs.

2. A shear clamp as set forth in claim 1, in which said clamping jaws have projections on their clamping surfaces engaging surfaces of the adjoining slabs.

3. A shear clamp as set forth in claim 1, in which said precast concrete slabs have longitudinally extending cylindrical voids receiving said jaws and the latter have a-rcuate clamping surfaces conforming to and engaging the curved walls of the voids.

4. A shear clamp as set forth in claim 1, in which said means includes -a bolt extending through the base portion and the .angularly disposed portion of the jaw and a nut behind the angularly disposed .port-ion threadingly engaging the bolt Whereby tightening said bolt draws said jaws into anchoring engagement with adjacent slabs.

5. A shear clamp as set forth in claim 4, in which an embossment is formed on the angularly disposed portion to receive said nut and prevent rotation thereof.

6. A shear clamp as set forth in claim 1, in which the precast slabs have cylindrical voids extending longitudinally .therethrough, said jaws having arcuate clamping surfaces with retaining projections thereon to engage the curved surfaces of the slabs within the voids, said base portion having an embossment with a central opening adjacent the angularly disposed clamping jaw, said angularly disposed portion having an embossment with a central opening therein adjacent the clamping portion of the jaw, and said drawing means including a threaded bolt extending through the openings in the embossment, and-a nut located behind the angularly disposed portion in the embossment therein threadingly engaging the bolt.

7. A shear clamp as set forth in claim 6, in which said angular-1y disposed portion is drawn into substantially parallel relation with the base portion when the clamping portion engages the wall surface of the void in the slab.

References Cited UNITED STATES PATENTS 944,022 12/1909 Eken 52-584 1,984,495 12/1934 Plym 52500 2,299,071 10/1942 Rogers 52586 2,680,250 6/1954 Kerby 52500 FOREIGN PATENTS 356,219 1905 France.

HEN-RY C. SUTHE'RIJAND, Primary Examiner.

FRANK L. ABBOTT, Examiner.

ROBERT A. STENZEL, Assistant Examiner. 

